This invention relates to a yarn break detecting device for a spinning machine, a weaving machine or the like, and more particularly to a yarn break detecting device which is adapted to be mounted on a spinning machine such as a ring spinning machine, a weaving machine or the like (hereinafter referred generally to as "spinning machine") to detect and display yarn break and subject predetermined control data to operation processing depending on the amount or degree of yarn break. Accordingly, the term "spinning machine" used herein indicates a spinning machine such as a ring spinning machine in a narrow sense, however, it indicates, in a broad sense, a weaving machine and the like as well as a spinning machine.
Conventionally, a variety of yarn break detectors of the electronic type which are constructed into different configurations based on various principles have been proposed and partially put into practice. Such conventional yarn break detectors of the electronic type are generally classified into a photoelectric system which is constructed so as to detect a yarn traveling between a light emitter and a light receptor and a piezoelectric system which is constructed so as to apply vibration due to tension of a yarn traveling to a piezoelectric element to detect traveling of the yarn.
Unfortunately, the photoelectric system, when it is used for detecting yarn break occurring in a spinning machine, causes restrictions to be imposed on arrangement of the light emitter and light receptor with respect to a yarn guide due to their configuration and results in malfunction due to adhesion of dust to an optical system. Also, the piezoelectric system has disadvantages of requiring to contact the system with a yarn and causing malfunction of the system due to mechanical vibration. Further, both systems are not suitable for detecting yarn break in a ring spinning machine because a yarn guide for spinning in the ring spinning machine is varied with time depending on the amount of a yarn spun.